SRSVs are a group of causative viruses of human viral gastroenteritis, the discovery of the first one of which goes back to 1972. They are known to cause infantile acute gastroenteritis and also outbreaks of food poisoning or the like among adults and preschool or elementary school children. Due to the inability to proliferate these SRSVs by cell culture and the lack of animal models capable of exhibiting sensitivity thereto, SRSV antigens and anti-SRSV antibodies are hardly available, resulting in a delay in the development of immunoserologic methods for the detection of the viruses.
Under such circumstances, it was succeeded to clone the gene of the Norwalk virus, an SRSV, in 1993, leading to the determination of the base sequence of its complete genomes [JP(PCT) 6-506823 A]. Subsequently, PCR methods which are useful to amplify apart of an RNA polymerase region were developed, and 14 SRSV-related viruses have been found to date. As a result of analyses of about 120 amino acids in these RNA polymerase regions, SRSVs are considered to be roughly differentiated into two genogroups, that is, Genogroup I including the Norwalk virus strain as a prototype and Genogroup II including the Snow Mountain virus strain as a prototype.
As genetic analyses of SRSV-related viruses proceeded, it came to knowledge that substantial diversity exists even in the same genogroup. As a matter of fact, it was found that with an RT-PCR method making use of primers for the genes of the Norwalk virus and Snow Mountain virus strains as the prototypes of the respective genogroups, every SRSV is not detectable and also that it is very difficult to design primers or set RT-PCT conditions for achieving efficient amplification of SRSVs.
In the meantime, antigens were prepared against some of the viruses, such as the Norwalk virus strain and the Snow Mountain strain, by genetic expression, antibodies were obtained, and ELISA-dependent SRSV detection methods making use of such antibodies were also developed. It was, however, still impossible to detect every gastroenteritis-causing SRSV due to the diversity of the SRSVs.
In Japan, on the other hand, SRSVs were designated in 1997 to be causative factors of food poisoning as defined in the Food Sanitation Act so that, if SRSV food poisoning breaks out, determination of its infection route is required. There is accordingly a desire for a method which easily and surely detects and identifies SRSVs in infected subjects' feces or foods.